1. Field of the Invention
The present invention relates to a method for the preparation of a powder of a rare earth oxide or, more particularly, to a method for the preparation of a powder of an oxide of a rare earth element consisting of particles having excellent dispersibility without agglomeration to be useful as a base material of a sintered ceramic body of a rare earth oxide or as a sintering aid of various kinds of ceramic materials such as silicon nitride, aluminum nitride and the like.
2. Description of the Related Art
In the prior art, an oxide powder of a rare earth element is conventionally prepared by the process in which an aqueous solution of an inorganic salt of the rare earth element is admixed with a water-soluble precipitant such as carbonates, oxalic acid or oxalates, hydroxides and the like to give a water-insoluble compound of the rare earth element such as a carbonate, oxalate, hydroxide and the like, respectively, and the precipitates of the water insoluble rare earth compound are collected by filtration, washed with water, dehydrated and dried and finally calcined so as to thermally decompose the rare earth compound into an oxide powder. It is unavoidable in this prior art method that the particles of the rare earth oxide cause agglomeration to form lumps or granules sometimes having a dimension of several millimeters. Therefore, disintegration of such agglomerates of the rare earth oxide particles is indispensable when the oxide powder is to be used in the above mentioned applications. A problem in conducting disintegration is that, even by undertaking the disintegration in a wet process by the addition of a wetting liquid and a dispersion work aid, fully dispersible rare earth oxide particles can hardly be obtained with a substantial amount of coarse particles or agglomerates even after a prolonged disintegration work which must be removed by screening so that the cost for the preparation of a rare earth oxide powder is necessarily increased.